<template>
  <div id="app">
    <div id="nav">
      <router-link to="/">待付款</router-link> 
      <router-link to="/a">待发货</router-link> 
      <router-link to="/b">已发货</router-link>
    </div>
    <router-view/>
  </div>
</template>

<style>
  #nav{
    width: 400px;
    display: flex;
    justify-content: center;
  }

  #nav a {
    width: 33.3333%;
    text-align: center;
    text-decoration: none;
    border: 1px solid #f40;
  }

    .box {
    width: 400px;
    height: 400px;
    text-align: center;
    line-height: 400px;
        border: 1px solid #f40;
  }

   .router-link-exact-active {
     background-color: rgb(21, 142, 223);
   }
</style>
